Twenty two school children and six adults died when their coach crashed into a wall in a motorway tunnel as they returned from a skiing holiday in Switzerland.

Investigations are ongoing, but police say the driver appears to have veered over the kerb and crashed with "extreme force" into the concrete wall marking the end of an emergency stop area inside the Sierre tunnel.

The ski party had been returning from a holiday in Val d'Anniviers, in the Valais Alps region on Tuesday. There were 52 people on board the coach, including 46 children aged about 12 from the Stekske primary school in Lommel, near the Dutch border, and from St Lambertus in Heverlee, near Leuven (Louvain).

Police say the coach had just left the resort on the journey home and joined the A9 motorway at the Bois de Finges roundabout near Sierre, heading towards Sion and Lausanne.

After about 2km, at 2015 GMT, the coach veered to the right inside the two-lane Sierre motorway tunnel, went over the kerb and into an emergency stop area.

The coach crashed head-on into the concrete wall where the emergency area ends, say police.

Twenty two children died and 24 others were injured - many suffering broken legs and arms. The two drivers and the children's four teachers were among the dead.

Although most of the victims are Belgian, Swiss officials say the dead include seven Dutch children. Among those injured are three Dutch, one Pole and one German.

Possible causes

Image caption
About 200 rescuers attended the accident

Immediately after the accident, emergency services closed the tunnel in both directions and the injured were airlifted to hospitals by helicopters and ambulances. Rescuers faced horrific scenes that left many traumatised by the experience, officials said. Some of the children had to be cut free from the wreckage.

Olivier Elsig, prosecutor for the Swiss state of Valais, said the cause of the crash was being investigated, but some scenarios could be ruled out.

He said CCTV footage showed that they could "categorically exclude" the possibility of a collision with another vehicle in the one-way tunnel.

The tunnel has a speed limit of 100km/h (62mph) but Mr Elsig said initial investigations suggested the coach was not speeding.

He said possible causes of the crash included a technical error, maybe the driver was feeling unwell or human error.

"An autopsy will enable us to confirm or refute the hypothesis of a whether the driver was suffering from a malaise or a health problem," he said.

The coach, which belonged to the Belgian Top Tours company, was a modern vehicle and the children were all wearing seatbelts, Mr Elsig said, but the force of the collision with the wall meant the belts could not save them.